Advanced Materials, Technology And Application - Proceedings Of The 2016 International Conference (Amta2016)

Proceedings of the 2016 International Conference on Advanced Materials, Technology and Application (AMTA2016)

Qingzhou Xu

• Publisher: WSPC
• Year: 2016
• eBook ISBN: 9789813200487
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

The 2016 International Conference on Advanced Materials, Technology and Application (AMTA2016) was held in Changsha, China on March 18–20, 2016. The main objective of the joint conference is to provide a platform for researchers, academics and industrial professionals to present their research findings in the fields of advanced materials and technology.The AMTA2016 received more than 150 submissions, but only 59 articles were selected to be included in this proceedings, which are organized into 7 chapters; covering Chemical Materials, composite and Nano Materials, Polymer and Concrete Materials, Structural Materials, Metal and Alloy Materials, Electrical Materials, and Biomaterials.

Chapter 1

Chemical Materials

The comparative study about chemical adsorption mechanism of
CO molecules on Al(101) surface

Qian Liao^1,b, Zheng-Xin Yan^*, Wei Liu, Yong-Shen Wang, An Gong,
Qian Chen and Shao-Hua Zhang

College of Science of Xi’an University of Science and Technology,
Xi’an 710054, China
E-mail: ^*[email protected],^b [email protected]

This research paper uses the Density functional theory of First-principles to investigate the chemadsorption mechanism at top site, bridge site and hollow site of CO on Al(101) surface, for favorable adsorption site. High electrical conductivity and good oxidation of high purity are mainly used in filling interface, materials design and electronics industries. It was important to discover the interaction mechanism between gas molecules and the Al(101) surface by analyzing the adsorption energy, density of states, electronic property and other properties by studying single molecule absorption systems. The results of the absorption energy, density of states and electronic properties show that the adsorption energy at bridge site is the smallest one,-0.2912 eV, the length of C-Al bond was shortened and the total Mulliken population significantly increased. Lastly, the most stable site of the CO adsorption of the surface is the bridge site.

Keywords: Density Functional Theory; Al (101) Surface; CO Molecule; Adsorption.

1. Introduction

Nano-micron aluminum powder is an important energetic material filler, because of its large surface area and high activity. The theoretical research and engineering application about the oxidation mechanism of aluminum surface are considered an important issue. High electrical conductivity and good oxidation of high purity is mainly used in filling interface, materials design and electronics industries.

In recent years, more and more research on Al adsorption surface has been studied extensively. For examples, Lei Xiaoli[1] et al. used the density functional theory to study the properties of structure, energy and electronic when H₂O and O₂ molecules is absorbed on Al(111) surface. They noted that the process about adsorption of H₂O and O₂ molecules on the Al(111) surface are divided into weak chemisorption and strong one Zhang Rong, Huang Kaiyou[2] et al. draw a conclusion that adsorption of Cl^- on a Al(100) surface is mainly the result of orbital interactions between 2s and 2p of Cl^- orbit and 3p orbit of basal metal by analyzing density of states of adsorption of Cl^- on different sites of clean Al(100) surface. Chen Yuhong, Cao Yijie[3] et al. investigated the absorption condition that H₂ molecules has been impacted on the pure Al(110) surface doped by Ti atoms, They have revealed that the H₂ molecules on pure Al(110) surface could not be dissociated, but it really exists a adsorption path to make the H₂ molecules dissociated when they are adsorbed on the Ti atoms above the top site of the Al(110) surface that Ti atoms were doped. However, studies on the adsorption characteristics of Al (110) surface are found rarely, and meanwhile it has significant meaning to understand its structure and properties in the study of catalytic when CO is mainly used as one of probe molecule[4,5,6]. Therefore, there is some value to study CO molecule on adsorption of the Al(101) surface.

In this paper, some molecular simulation and calculation were done on the base of the theory of First-principles method to explore three typical adsorption sites: top, bridge and hollow site when the CO molecules are affected on Al(101) surface. It will have important reference significance to discover the interaction mechanism between gas molecules and the Al(101) surface by analyzing the adsorption energy, density of states, electronic property and other properties by studying single molecule absorption systems.

2. Calculation

Three kinds of chemisorption sites about adsorption of CO on the Al(101) surface are built and calculated by the Castep module of Material Studio software on the base of first-principles density functional theory (DFT). The interaction between the valence electron and ion core is depicted by the PAW (Projector Augmented Wave), and the relevant parts of electronic exchange are described by the the standard exchange-correlation functional method called PBE[3] in the generalized gradient approximation (GGA). The method of integration in brillouin zone is the Monkhorst-Pack to calculate the special k-point mesh point. During the calculation, k-point grid size is set to 441, the cutoff of energy is set to 400eV and the creation of energy convergence is set to 210-5eV. The setting above well meet the computational accuracy requirements through convergence test. To make the quantity of calculation for every surface affected by other one less, the selected super-cell is the size of 221, the thickness of plane model is five atomic layers, and the thickness of vacuum zones along the Z-direction is 10Å. The results of Zang Lili[7,8] et al. is referred to set the length of bond of C-O and C-Al as 1.15Å and 1.90Å. The top layer of atoms around the balanced position is only allowed to be relax and other atoms is fixed during the adsorption of CO on the Al(101) surface. As a result, the influence of dipole moment from atoms in the lowest layer becomes small as soon as possible and meantime the quantity of calculation is decreased.

3. Result and Discuss

As the figure 1 depicts, the bond length and bond angle of Al-C-O has been changed after the adsorption of CO on the Al(101). The bond lengths of Al-C-O are all stretched for three different adsorption sites and the bond angle is turned into133.322 relative to 130.050 before optimization, which is optimized to achieve a stable state.

Not only considering the type of orientation accumulation and the second time symmetrical structure to the Al (101) crystal, but also its parameters of the model(bond length, lattice constants, et al.) decide three possible sites that the adsorption of CO molecules on the Al(101) surface: top, bridge and hollow sites. Also the inner properties of CO that the electronic negative property of carbon atom is lower than the oxygen atom lead to the latter always provide the charges for the former. The result is the charge property of carbon atoms has shown negative and the oxygen atom is positive, and therefore it often occurs that the carbon atom is bonded to the metal atom when the CO molecules is absorbed on the metal surface[9]. The adsorption model case is shown in Figure 1. Adsorption energy for every site in the adsorption process is calculated and the relevant density of states and charge density difference are analyzed based upon the results of above.

3.1. Adsorption energy

It will release some of the energy when gas is adsorbed on one interface, and the energy is called adsorption energy. In the same context, the adsorption energy can reveal the stable characteristics of the gas molecules adsorbed on the surface of the material, the lower its energy the stronger its adsorption capacity and the more stable its system. According to the changes of the total system energy before and after the adsorption, the energy of system is defined as follows [10]:

E_chem is the energy of adsorption of CO on the Al(101); E_CO/Al(101) represents the total adsorption energy for the whole system; E_Al(101) is the meaning of energy of Al (101) surface that a single ce...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• Preface
• Committees
• Keynote Speech
• Table of Contents
• Chapter 1 Chemical Materials
• Chapter 2 Composite and Nano Materials
• Chapter 3 Polymer and Concrete Materials
• Chapter 4 Structural Materials
• Chapter 5 Metal and Alloy Materials
• Chapter 6 Electrical Materials
• Chapter 7 Biomaterials
• Author Index